Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

to all maths geniuses...!!!!?

i have some questions on differentiation...

find dy/dx when

1) y=1/x

2) y=3/x2

3) y=x to the power of 3/4

4) y=1/2x

5) y=3x to the power of 4 - 1/square root of x

6) y=1/x + 2/3x

find gradient of the curve for the x value stated

7)y = x3 – 3x2 + 5x – 12 when x = 2

8)y = √x+ 2x when x = 9

9)y = 1/x2 – 3x2 when x = 2

10points to the most answered question.... tnx

4 Answers

Relevance
  • 1 decade ago
    Favorite Answer

    1) y = 1/x

    This can be written as x^(-1). Bring the exponent down as a coefficeint and subtract one to the exponent to get:

    (-1)*x^(-2) which can be written as:

    dy/dx = -1/(x^2)

    2) y = 3/(x^2)

    This can be written as 3*x^(-2). Bring the exponent down as a coefficeint and subtract one to the exponent to get:

    -2*3*x^(-3) which can be written as:

    dy/dx = -6/(x^3)

    3) y = x^(3/4)

    Bring the exponent down as a coefficeint and subtract one to the exponent to get:

    (3/4)*x^(-1/4)

    This can be written as:

    dy/dx = 3 / (4* x^(1/4))

    4) y = 1/2x

    Bring the exponent down as a coefficeint and subtract one to the exponent to get:

    1*(1/2)*x^0

    x^0 is always = 1, so, this would be: 1*(1/2)*1

    dy/dx = 1/2

    5) y = 3x^4 - 1/(x^(1/2))

    The first term should be the same as before, and you get 12*x^3.

    The second term can be rewritten as x^(-1/2), which become: (-1/2)*x^(-3/2). This can be written as (-1 / (2x^3/2))

    Then write out the equation as:

    dy/dx = 12*x^3 + (1 / (2x^3/2))

    6) y = 1/x + 2/(3x)

    The first term is just like problem 1: -1/(x^2)

    The second term can be written as 2*(3x^-1). Bring the exponent down as a coefficeint and subtract one to the exponent to get: -1*2*(3x^-2), also known as

    dy/dx = -1/(x^2) - 2/(3x^2)

    7) x3 – 3x2 + 5x – 12 when x = 2

    Take the derivative and plug in whatever is given as x:

    dy/dx = 3x^2 - 6x + 5

    y'(2) = 3(2)^2 - 6(2) + 5

    = 12 - 12 + 5

    = 5

    8) y = x^(1/2) + 2x when x = 9

    The derivative is:

    dy / dx = 1/(2x^(1/2)) + 2

    y'(9) = 1/(2*9^(1/2)) + 2

    = 1/6 + 2

    = 13/6

    9) 1/(x^2) - 3x^2 when x = 2

    The derivative is:

    -2/(x^3) - 6x

    y'(2) = -2/(2^3) - 6(2)

    = -2/8 - 12

    = -1/4 - 12

    = -49/4

  • Anonymous
    1 decade ago

    You will love wolframalpha.com. It can do all that for you.

    "Find the derivative of 1/x dy"

    Press enter.

    The gradient is the same thing as a slope.

    1. Graph the equation.

    2. Find the y value at the point on the graph from the given x value.

    Gradient = change in y / change in x

    Source(s): Google
  • Rick
    Lv 5
    1 decade ago

    1) y = x^-1 dy/dx = -x^-2 = -1/x^2

    2) y = 3(x^-2) dy/dx = -6(x^-3) = -6/x^3

    3) y = x^(3/4) dy/dx = 3/4(x^-1/4)

    4) dy/dx = 1/2

    5) I assume you mean: y = 3x^4 - x^-1/2 ao dy/dx = 12x^3 +1/2x^-3/2

    6) dy/dx = -x^-2 + 2/3

    7) dy/dx=3x^2 -6x +5 at x = 2 dy/dx = 12-12+5 = 5

    8) dy/dx =1/2x^-1/2 + 2 at x=9 dy/dx = 1/6 +2 = 2 1/6

    9) dy/dx = -2x^-3 -6x at x=2 dy/dx = -1/4 -12 = -12 1/4

    yaw

  • 1 decade ago

    1) derivative = -1/(x^2)

    2) derivative = -6/(x^2)

    3) derivative = (3/4)(x^(-1/4)) or simpler 3 divided by (4 x 4th root x)

    4) derivative = -1/((2x)^2)

    5) derivative = 3x^(4-(1/sqrtx)) (ln(3x)+1) *im not totally sure about this

    6) derivative = -5/(3x^2)

    btw for 5 i thought meant y = 3x^(4-(1/sqrt x))

    unfortunaltely idk what the **** a fgradient is so good luck with that

    Source(s): source? not much of one. first year University student i guess singapore? no way im from there
Still have questions? Get your answers by asking now.